1. Field of the Invention
The present invention relates to a rapidly soluble solid in the oral cavity, particularly, a rapidly soluble preparation in the oral cavity. Also, the present invention relates to a process for producing the same.
2. Background Art
Recently, a novel dose form has been sought for patients having difficulty in swallowing, such as the aged, infants and the like. For example, disintegrating preparations in the oral cavity, jellies, and pastes have been suggested. Particularly, disintegrating preparations in the oral cavity, which can easily be taken without water in any place at any time, would be suitable for the aged, infants and the like.
Generally, disintegration properties and hardness of tablets conflicts with each other. To increase the rate of disintegration for improving disintegration properties leads to decreased tablet hardness. However, it is important for tablets to have a certain degree of hardness while the tablets are transported and packaged in factories or distributed through the market or when a patient takes the tablet out of the package. A tablet having insufficient hardness fails to retain its shape and can crumble in these situations.
Under these circumstances, various techniques for producing rapidly soluble preparations in the oral cavity have been proposed.
For example, JP-B-58-24419 (the term "JP-B" as used herein means an "examined Japanese patent publication") discloses a process for producing easily disintegrating porous tablets which comprises mixing a pharmaceutical composition with a solvent capable of freezing and inert to the composition, solidifying the solvent in an inert cooling medium, compressing the mixture into tablets at a temperature lower than the freezing point of the solvent, and evaporating the solvent by freeze-drying or spontaneous drying.
Commercially available rapidly soluble preparations in the oral cavity include Zydis (commercial name) produced by R. P Scherer (England), which is produced by dissolving an active ingredient, a polymer, a saccharide, and the like, followed by freeze-drying.
Additionally, JP-A-5-271054 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a tablet soluble in the oral cavity and its preparation; JP-A-8-291051 discloses a method for producing rapidly soluble tablet and a rapidly soluble tablet produced by the method; JP-A-8-333243 discloses a tablet having excellent touch in the oral cavity; and JP-A-9-48726 discloses a rapidly disintegrating preparation in the oral cavity and its production.
The techniques disclosed in the above references have their several disadvantages such that the rate of disintegration is insufficient; the tablets, while capable of disintegrating rapidly, fail to have sufficient mechanical strength; or the finished tablets are difficult to handle ordinarily due to high hygroscopicity.
In molding a pharmaceutical composition into solid preparations, such as tablets and the like, a rotary tablet machine is used usually. When a pharmaceutical composition in semi-solid or wet conditions is molded into tablets by using this type of tablet machine, such problems often occur as poor fluidity of the composition to be supplied and adhesion of the composition to a pressing member.
Water-soluble binders (e.g., polyvinylpyrrolidone, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, polyvinyl alcohol, methyl cellulose, gelatin, and the like) are used to increase hardness of tablets. Disintegrants, such as hydroxypropyl cellulose having a low degree of substitution, corn starch, alginic acid, and the like, are used to increase the rate of disintegration. When used in increased amounts; however, the water-soluble binders or disintegrants become sticky as the tablet crumbles in the oral cavity or make the tablet unpleasant to palate.